Subversion Repositories mkgmap

/*
 * Copyright (C) 2008 Steve Ratcliffe
 * 
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2 as
 *  published by the Free Software Foundation.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 * 
 * 
 * Author: Steve Ratcliffe
 * Create date: 01-Jul-2008
 */
package uk.me.parabola.mkgmap.general;

import java.util.List;

import uk.me.parabola.imgfmt.app.Area;
import uk.me.parabola.imgfmt.app.Coord;
import uk.me.parabola.util.Java2DConverter;

/**
 * Clip a polygon to the given bounding box.  This may result in more than
 * one polygon.
 *
 * @author Steve Ratcliffe
 */
public class PolygonClipper {

        /**
         * Clip the input polygon to the given area.
         * @param bbox The bounding box.
         * @param coords The coords of the polygon.
         * @return Return null if the polygon is already completely inside the
         * bounding box.
         */
        public static List<List<Coord>> clip(Area bbox, List<Coord> coords) {
                if (bbox == null)
                        return null;

                // If all the points are inside the box then we just return null
                // to show that nothing was done and the line can be used.  This
                // is expected to be the normal case.
                boolean foundOutside = false;
                for (Coord co : coords) {
                        if (!bbox.contains(co)) {
                                foundOutside = true;
                                break;
                        }
                }
                if (!foundOutside)
                        return null;

                java.awt.geom.Area bbarea = Java2DConverter.createBoundsArea(bbox); 
                java.awt.geom.Area shape = Java2DConverter.createArea(coords);

                shape.intersect(bbarea);

                return Java2DConverter.areaToShapes(shape);
        }

}